Universal Compiling and (No-)Free-Lunch Theorems for Continuous-Variable Quantum Learning

Tyler Volkoff, Zoë Holmes, Andrew Sornborger

Research output: Contribution to journalArticlepeer-review

11 Scopus citations


Quantum compiling, where a parameterized quantum circuit is trained to learn a target unitary, is an important primitive for quantum computing that can be used as a subroutine to obtain optimal circuits or as a tomographic tool to study the dynamics of an experimental system. While much attention has been paid to quantum compiling on discrete-variable hardware, less has been paid to compiling in the continuous-variable paradigm. Here we motivate several, closely related, short-depth continuous-variable algorithms for quantum compilation. We analyze the trainability of our proposed cost functions and numerically demonstrate our algorithms by learning arbitrary Gaussian operations and Kerr nonlinearities. We further make connections between this framework and quantum learning theory in the continuous-variable setting by deriving no-free-lunch theorems. These generalization bounds demonstrate a linear resource reduction for learning Gaussian unitaries using entangled coherent-Fock states and an exponential resource reduction for learning arbitrary unitaries using two-mode-squeezed states.

Original languageEnglish
Article number040327
JournalPRX Quantum
Issue number4
StatePublished - Dec 2021
Externally publishedYes


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